1. Field
The disclosed concept pertains generally to fuses. The disclosed concept also pertains to expulsion type fuses.
2. Background Information
Fuses, such as for example, medium voltage fuses, have traditionally used silver or other metal conductors as fusible element material. The size of the cross-section of the fusible element determines the maximum current that can be passed through the fusible element before melting. When relatively low amperage rated fuses are needed, fusible elements with relatively smaller cross-sections are employed. As the cross-section of the fusible element is reduced, the strength of the fusible element is also reduced.
Some fuses also incorporate blown fuse indicators such as a mechanical spring indicator or a chemically activated indicator. In one prior fuse, which uses a mechanical spring indicator, a fusible element is used to bias a spring. When the fusible element breaks, the spring is released which in turn deploys an indicator to indicate that the fuse is blown. In another prior fuse, which uses a chemically activated indicator, a fusible element is used to bias a firing pin. When the fusible element breaks, the firing pin is released which in turn causes a small explosion that deploys an indicator to indicate that the fuse is blown. In both the mechanical spring indicator and the chemically activated indicator, tension is applied to the fusible element. However, as the amperage rating of the fuse is reduced, the strength of the fusible element is also reduced. At relatively low amperage ratings, the tension applied to the fusible element by the mechanical spring indicator or the chemically activated indicator can cause the fusible element to prematurely break.
Expulsion type fuses face a similar difficulty. In one prior expulsion type fuse, tension is applied to the fusible element by a spring such that when the fusible element breaks, the spring pulls the portions of the fusible element away from each other. However, as the amperage rating of the fuse is reduced, the strength of the fusible element is also reduced. When the amperage rating of the fuse becomes too low, the tension applied by the spring can cause the fusible element to prematurely break.
It thus would be desirable to provide an improved fuse that overcomes these and other shortcomings associated with the relevant art.